I have been intrigued by the enormous importance of metal-ions as essential cofactors for many different biological processes, including gene regulation, free radical homeostasis, and innumerable other catalytic reactions. DMT1 (previously known as DCT1), which I recently cloned is a transmembrane transporter that accepts a variety of transition metal ions. Naturally occurring mutants in DMT1 have provided compelling evidence that it plays a major role in intestinal and bone marrow iron uptake. However, as I describe in the Research Plan section, we hypothesize that there must exist at least one additional transmembrane iron transporter that is different from DMT1. We postulate that this putative transporter, DMT2, mediates liver iron accumulation in the setting of iron overload. This hypothesis is supported by previous reports and my preliminary data. Therefore, my immediate objective is to isolate this candidate transporter, DMT2, to better understand iron metabolism and regulation in normal and disease states. To do this, I will combine expression cloning technology that I have used previously along with analysis of mouse models generated in the laboratory where I am currently working. The work under KO1 support on liver iron transport will be performed in the outstanding environment provided by Harvard Medical School and the Howard Hughes Medical Institute in the laboratory of Dr. Andrews at Children's Hospital. She is an expert in mouse molecular genetics and the medical implications of iron metabolism. Her laboratory, collaborators and colleagues in the local community will help me to develop the skills in a variety of methodologies, including transgenic mouse technology. My research career had been interrupted previously by my teaching obligations in Japan. By resigning from my post there, I have made a total commitment to establish an independent career as a research scientist. This KO1 support from NIDDK will be a stepping stone toward that goal. The proposed project will be carried out in a superb training environment which will nurture my long-term career goal to understand the roles of metal-ions in health and disease.